Method for preparing 2,3-dichloro-5-trifluoromethylpyridine with high selectivity

ABSTRACT

A method for preparing 2,3-dichloro-5-trifluoromethylpyridine, comprising at a temperature of 100˜150° C. and a pressure of 0.5˜5.0 MP, in presence of at least one catalyst selected from supported metal chloride, supported zeolite molecular sieve and supported heteropolyacid, 2-chloro-5-trifluoromethylpyridine reacts with chlorine gas to obtain 2,3-dichloro-5-trifluoromethylpyridine. The preparing method provided by the present invention has advantages such as high selectivity of desired product, high utilization rate of chlorine gas, moderate process condition, simple operation and less three wastes. The present invention also discloses a preparing method for preparing 2-chloro-5-trifluoromethylpyridine, which is capable of reducing unit consumption, reducing separation cost, and improving safety compared to the prior art.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.16/620,763, filed on Dec. 9, 2019, for which priority is claimed under35 U.S.C. § 120; and this application claims priority of InternationalApplication No. PCT/CN2018/119312 filed on Dec. 5, 2018, PatentApplication No. 201711275197.X filed in China on Dec. 6, 2017, PatentApplication No. 201810009294.2 filed in China on May 1, 2018, PatentApplication No. 201810009301.9 filed in China on May 1, 2018, and PatentApplication No. 201810020465.1 filed in China on May 1, 2018, the entirecontents of all of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method for preparingchlorotrifluoromethylpyridine, specifically it relates to a method forpreparing 2,3 -dichloro-5 -trifluoromethylpyridine.

BACKGROUND

Fluorine-containing, heterocycle, and chirality are three big featuresof the modern agricultural chemicals and new drugs in the medicinefield. In recent years, new agrochemicals of fluorine-containingpyridines, such as chlorfluazuron, fluazuron, haloxyfop and fluazinametc. have advantages such as broad-spectrum and systemic, highefficiency and low toxicity, and less pollution, thus they have becomethe major varieties of the highly efficient pesticide, herbicide andfungicide. 2,3-dichloro-5-trifluoromethylpyridine (2,3,5-DCTF) is a keyintermediate for producing these new agrochemicals, it has become a hotpoint of the industry.

For the synthesis of 2,3-dichloro-5-trifluoromethylpyridine, thereexists the following disclosures in the prior art:

(1) European Patent EP0078410 reports a method, wherein a fluidized bedis used as a reactor, in presence of FeCl₃/AC catalyst, a chlorinationreaction takes place at 250° C. between2-chloro-5-trifluoromethylpyridine and chlorine gas, to produce2,3-dichloro-5-trifluoromethylpyridine. The yield of this method canreach 74%, but multiple isomers are produced in a gas phase chlorinationreaction, as a result the products are difficult to separate;

(2) U.S. Pat. No. 4,420,618 reports a method for preparing2,3-dichloro-5-trifluoromethylpyridine by an atmospheric liquid phasechlorination process, wherein in presence of a metal chloride catalyst,2-chloro-5-trifluoromethylpyridine reacts with chlorine gas to produce2,3-dichloro-5-trifluoromethylpyridine. The yield of this method is16˜75%, the catalyst amount is very large and needs to reach 40˜200% ofmass of the raw material, it is required to continuously introducechlorine gas during the reaction process, the utilization efficiency ofchlorine gas is low, resulting in a high production cost. In thedisclosed prior art, the gas phase chlorination method has disadvantagessuch as low selectivity of 2,3-dichloro-5-trifluoromethylpyridine, muchof by-product isomers, difficulty to separate, and the liquid phasechlorination method has disadvantages of large catalyst amount, lowchlorine gas utilization rate. Therefore, it is necessarily make furtherimprovements to the preparing method of 2,3 -dichloro-5-trifluoromethylpyridine.

SUMMARY

In view of the shortcomings of the prior art, the present inventionprovides a method for preparing 2,3-dichloro-5-trifluoromethylpyridineby a pressurized liquid phase chlorination, the method hascharacteristics such as high selectivity of desired product, highutilization rate of chlorine gas, moderate process condition, simpleoperation and less three wastes.

The names and abbreviations of the raw materials and products accordingto the present invention are as follows:

-   -   2,5 -CTF: 2-chloro-5-trifluoromethylpyridine;    -   3,5-CTF: 3-chloro-5-trifluoromethylpyridine;    -   2,3,5-DCTF: 2,3-dichloro-5-trifluoromethylpyridine;    -   2,6,3-DCTF: 2,6-dichloro-3-trifluoromethylpyridine;    -   2,3,6,5-TCTF: 2,3,6-trichloro-5-trifluoromethylpyridine.    -   3-TF: 3-trifluoromethylpyridine;    -   3-MP: 3-methylpyridine;    -   2,3-CTF: 2-chloro-3-trifluoromethylpyridine;

For the preparing method provided by the present invention, its chemicalreaction formula is as follow:

The present invention provides a technical solution as follow:

A method for preparing 2,3-dichloro-5-trifluoromethylpyridine, themethod comprises:

At a temperature of 100˜150° C. and a pressure of 0.5˜5.0MPa, inpresence of a first catalyst, 2-chloro-5-trifluoromethylpyridine reactswith chlorine gas to obtain 2,3 -dichloro-5 -trifluoromethylpyridine;

the first catalyst is at least one selected from supported metalchloride, supported zeolite molecular sieve and supportedheteropolyacid.

For the supported metal chloride, its active components are at least oneselected from WCl₆, MoCl₅, FeCl₃, AlCl₃, CuCl₂, ZnCl₂, SnCl₄, and SbCl₅,and the load of the active components is 1-50wt %,

For the supported zeolite molecular sieve, its zeolite molecular sieveis at least one selected from ZSM-5, Beta, X, Y, 5A and L type zeolitemolecular sieve, and the load of the zeolite molecular sieve is 1˜50 wt%,

For the supported heteropolyacid, its heteropolyacid is at least oneselected from phosphotungstic acid, silicotungstic acid, phosphomolybdicacid and silicomolybdic acid, and the load of the heteropolyacid is1-50wt %.

In the method for preparing 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention, using2-chloro-5-trifluoromethylpyridine and chlorine gas as the raw material,reacts in presence of the first catalyst, to obtain2,3-dichloro-5-trifluoromethylpyridine. For the first catalyst used,metal chloride, zeolite molecular sieve or heteropolyacid are supportedon a carrier, to provide dispersion of the active components, making itsuitable for the reaction for preparing2,3-dichloro-5-trifluoromethylpyridine using2-chloro-5-trifluoromethylpyridine and chlorine gas as the rawmaterials, and the selectivity of the desired compound2,3-dichloro-5-trifluoromethylpyridine can be significantly increased.

The first catalyst used in the present invention is at least oneselected from supported metal chloride, zeolite molecular sieve andheteropolyacid .

When the first catalyst is a supported metal chloride, its activecomponents are at least one selected from WCl₆, MoCl₅, FeCl₃, AlCl₃,CuCl₂, ZnCl₂, SnCl₄, and SbCl₅.

Preferably, the active components are at least one selected from WCl₆,MoCl₅, ZnCl₂, FeCl₃.

In the supported metal chloride, the load of the active component ispreferably 1˜50 wt %.

Further preferably, the load of the active components is 5˜20 wt %.

When the first catalyst is a supported zeolite molecular sieve, thezeolite molecular sieve is at least one selected from ZSM-5, Beta, X, Y,5A and L type zeolite molecular sieve.

Preferably, the zeolite molecular sieve is at least one selected fromZSM-5, Beta, L.

For the zeolite molecular sieve, its Si/Al ratio may be one thatfacilitates the reaction. Preferably, Si/Al ratio of the zeolitemolecular sieve is 200 or less, and the counter cation is at least oneselected from H⁺, alkali metal ion, alkaline earth metal ion, transitionmetal ion and rare earth metal ion.

For the supported zeolite molecular sieve, the load of the zeolitemolecular sieve is preferably 1˜50wt %.

Further preferably, the load of the zeolite molecular sieve is 5˜20wt %.

When the first catalyst is a supported heteropolyacid, theheteropolyacid is at least one selected from phosphotungstic acid,silicotungstic acid, phosphomolybdic acid and silicomolybdic acid.

In the supported heteropolyacid, the load of the heteropolyacid ispreferably 1˜50wt %.

Further preferably, the load of the heteropolyacid is 5˜20wt %.

The carrier used in the first catalyst according to the presentinvention is preferably at least one selected from silicon dioxide,alumina, titania, zirconia, activated carbon, silicon carbide andmesoporous molecular sieve.

For the method for preparing 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention, the amount of the catalyst may be onethat facilitates the reaction.

Preferably, the amount of the first catalyst is 0.1˜30wt % of the massof 2-chloro-5-trifluoromethylpyridine.

Further preferably, the amount of the first catalyst is 5˜20wt % of themass of 2-chloro-5 -trifluoromethylpyridine.

In the method for preparing 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention, the ratio of raw material chlorinegas to 2-chloro-5-trifluoromethylpyridine may be one that facilitatesthe reaction.

Preferably, the molar ratio of the chlorine gas to2-chloro-5-trifluoromethylpyridine is 0.5˜10:1.

Further preferably, the molar ratio of the chlorine gas to2-chloro-5-trifluoromethylpyridine is 1˜3:1.

In the method for preparing 2,3-dichloro-5-trifluoromethylpyridineofprovide by the present invention, the reaction pressure needs to be onethat facilitates the reaction.

Preferably, the reaction pressure is 0.5˜5.0MPa.

Further preferably, the reaction pressure is 1.0˜2.0MPa.

For the method for preparing 2,3-dichloro-5-trifluoromethylpyridine ofprovided by the present invention provide, the reaction temperature maybe one that facilitates the reaction.

Preferably, the reaction temperature is 100˜150° C.

For the method for preparing 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention, preferably the reaction is conductedin an autoclave. For the autoclave, its material is preferably selectedfrom 316L, Monel alloy, Inconel alloy or Hastelloy alloy.

For the method for preparing 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention, after the reaction is finished, analkaline solution can be firstly added, then separated to obtain2,3-dichloro-5-trifluoromethylpyridine.

the alkaline solution can be an organic base and/or an inorganic basethe organic base is preferably at least one selected from dimethylamine,diethylamine, triethylamine, dipropylamine and tripropylamine. theinorganic base is preferably at least one selected from NaOH, Na₂CO₃,NaHCO₃, KOH, K₂CO₃, KHCO₃ and aqueous ammonia.

For 2,3-dichloro-5-trifluoromethylpyridine prepared by the presentinvention, a qualitative analysis can be conducted by GC-MS, and aquantitative analysis can be conducted by gas chromatography internalstandard method.

The calculating formulas for the conversion of2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the product 2,3-dichloro-5-trifluoromethylpyridine according tothe present invention are as follows:

(1) conversion of 2,5-CTF: X2,5-CTF=moles of 2,5-CTF consumed during thereaction/moles of 2,5-CTF added to the reactor×100%;

(2) selectivity of the product i: Si=moles of the product i/moles of2,5-CTF consumed during the reaction×100%;

(3) yield of the product i: Yi=X_(2,5-CTF×)S_(i)=moles of the producti/moles of 2,5-CTF added to the reaction×100%,

Wherein, i represents a product such as 2,3,5-DCTF, 2,6,3-DCTF and2,3,6,5-TCTF etc.

Compared to the prior art, the method for preparing2,3-dichloro-5-trifluoromethylpyridine provided by the present inventionhas the advantages as follows: high selectivity and yield of the desiredproduct 2,3-dichloro-5-trifluoromethylpyridine, and they can reach 90%or more; small catalyst amount, and easy to separate with the reactants,it can realize recycling of the catalyst; without need to use an organicsolvent, low cost, and high utilization efficiency of chlorine gas.

Further, in order to reduce unit consumption, to reduce separation cost,and to improve safety, the present invention also provides the followingmethod for preparing 2-chloro-5-trifluoromethylpyridine.

A method for preparing 2-chloro-5-trifluoromethylpyridine, the method isa two-stage method, comprising:

(1) chlorofluorination reaction: in presence of a chlorofluorinationcatalyst, the chlorofluorination temperature is maintained at 150˜320°C., 3-methylpyridine, chlorine gas and hydrogen fluoride are introducedinto the chlorofluorination reaction region, to obtain a mixed gascomprising 3-trifluoromethylpyridine;

(2) chlorination reaction: in presence of the chlorination catalyst, thechlorination temperature is maintained at 220˜380° C., the mixed gascomprising 3-trifluoromethylpyridine obtained in step (1) is introducedinto the chlorination reaction region, to obtain2-chloro-5-trifluoromethylpyridine, the chlorination catalyst isselected from fluoride, oxide, hydroxide, carbonate or chloride ofmagnesium, calcium, barium, a palladium catalyst supported on activatedcarbon, alumina or aluminium fluoride.

The above-mentioned preparing method provided by the present inventionis a two-stage method reaction, comprising chlorofluorination reactionstep and chlorination reaction step. Wherein, in the chlorofluorinationreaction step, it is required to use a chlorofluorination catalyst.

the chlorofluorination catalyst can be a common chlorofluorinationcatalyst in the art.

As a preferred embodiment, the chlorofluorination catalyst includes amain catalyst, a first co-catalyst and a second co-catalyst; the maincatalyst is at least one selected from aluminium, magnesium andchromium, the first co-catalyst is at least one selected from iron,cobalt, manganese, nickel, copper, bismuth and zinc, and the secondco-catalyst is at least one selected from lanthanium, cerium, barium,calcium, sodium and potassium.

As a further preferred embodiment, in the chlorofluorination catalyst,the main catalyst is selected from aluminium and/or chromium, the firstco-catalyst is at least one selected from iron, nickel and copper, andthe second co-catalyst is at least one selected from lanthanium, bariumand calcium.

In the chlorofluorination catalyst, the ratio among the main catalyst,the first co-catalyst and the second co-catalyst may be one thatfacilitates the reaction.

Preferably, the molar ratio among the main catalyst, the firstco-catalyst and the second co-catalyst is 50˜95:5˜42:0.3˜8.

Further preferably, the molar ratio among the main catalyst, the firstco-catalyst and the second co-catalyst is 75˜90:10˜20:1˜5.

For the preparing method provided by the present invention, in step (1)of chlorofluorination reaction step, the ratio among the raw material3-methylpyridine, chlorine gas and hydrogen fluoride may be one thatfacilitates the reaction.

Preferably, the molar ratio among the 3-methylpyridine, chlorine gas andhydrogen fluoride is 1:0.1˜50:1˜30.

Further preferably, the molar ratio of among the 3-methylpyridine,chlorine gas and hydrogen fluoride is 1:4˜10:3˜12.

Wherein, the raw material 3-methylpyridine can be directly added to thereaction in a form of gas, and it also can be added to the reaction in aform of mixed gas after inert gas dilution.

Preferably, the 3-methylpyridine is a mixed gas after inert gasdilution.

Wherein, the proportion of 3-methylpyridine in the mixed gas after inertgas dilution may be one that facilitates the reaction.

Preferably, the molar ratio of the 3-methylpyridine to the mixed gas is1:0.5˜50.

Further preferably, the molar ratio of the 3-methylpyridine to the mixedgas is 1:5˜20.

For the preparing method provided by the present invention, in step (1)of chlorofluorination reaction, the contact time of the raw material3-methylpyridine, chlorine gas and hydrogen fluoride with thechlorofluorination catalyst may be one that facilitates the reaction.

Preferably, the contact time of the 3-methylpyridine, chlorine gas andhydrogen fluoride with the chlorofluorination catalyst is 0.5˜40 s.

Further preferably, the contact time of the 3-methylpyridine, chlorinegas and hydrogen fluoride with the chlorofluorination catalyst is 1.5˜20s.

For the preparing method provided by the present invention, in step (2)of chlorination reaction, the chlorination catalyst used is selectedfrom fluoride, oxide, hydroxide, carbonate or chloride of magnesium,calcium, barium, a palladium catalyst supported on activated carbon,alumina or aluminium fluoride.

the fluoride, oxide, hydroxide, carbonate and chloride of magnesium,calcium, barium can be magnesium fluoride, calcium fluoride, bariumfluoride, magnesium oxide, calcium oxide, barium oxide, magnesiumhydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate,calcium carbonate, barium carbonate, magnesium chloride, calciumchloride, and barium chloride.

the supported palladium catalyst being supported on activated carbon,alumina or aluminium fluoride can be a supported palladium catalystbeing supported on activated carbon, a supported palladium catalystbeing supported on alumina, a supported palladium catalyst beingsupported on aluminium fluoride.

Preferably, the chlorination catalyst is selected from fluoride, oxideor chloride of magnesium, calcium, a supported palladium catalyst beingsupported on activated carbon or aluminium fluoride.

For the preparing method provided by the present invention, in step (2)of chlorination reaction, the contact time of the mixed gas comprising3-trifluoromethylpyridine with the chlorination catalyst may be one thatfacilitates the reaction.

Preferably, the contact time of the mixed gas comprising3-trifluoromethylpyridine with the chlorination catalyst is 0.5˜40 s.

Further preferably, the contact time of the mixed gas comprising3-trifluoromethylpyridine with the chlorination catalyst is 1.5˜20 s.

The preparing method provided by the present invention is a two-stagetype method, comprising chlorofluorination reaction step andchlorination reaction step, a temperature control between the two stepshas an influence on the reaction results.

Preferably, the chlorofluorination temperature is 150˜320° C., and thechlorination temperature is 220˜380° C.

Further preferably, the chlorofluorination temperature is 220˜260° C.,and the chlorination temperature is 270˜320° C.

The preparing method provided by the present invention is preferablyconducted in a fixed bed or fluidized bed reactor.

For the preparing method provided by the present invention, calculatingformulas of the yield of each compounds are as follows:

Yield of product i: Y_(i)=(m_(i)/M_(i))/(m_(3-MP)/M_(3-MP))×100%,

Yield of other products: Y_(other)=(1-ΣY_(i))×100%,

Wherein i represents four substances such as 3-TF, 2,5-CTF, 2,3-CTF,2,6,3-DCTF etc., the other products include the by-products in whichmethyl group on side chain is insufficiently chlorofluorinated and thering is excessively chlorinated, and substances lost in the experimentalprocedure. Since under the given reaction condition, in each followingexamples the conversions of 3-methylpyridine are all 100%, in thepresent invention the yield of the product i is the selectivity of theproduct i.

Compared to the previous method, The above preparing method of2-chloro-5-trifluoromethylpyridine has advantages as follows: improvingthe selectivity and the yield of the desired product2-chloro-5-trifluoromethylpyridine by designing and usingchlorofluorination catalyst and chlorination catalyst, the selectivityand the yield of 2-chloro-5-trifluoromethylpyridine are up to 76.7%; thegas from the first stage reaction region directly enters into the secondstage reaction region for reaction, without operations of cooling,separation, and revaporization, the operation is simple, the energyconsumption is reduced; by the two-stage type reaction, the temperatureof each stage reaction is low, and the content of the by-products issmall.

The present invention also provides the following method for preparing2-chloro-5-trifluoromethylpyridine, it has characteristics such as highraw material conversion, high selectivity of desired product, lowreaction temperature, low energy consumption, easy to separate, withoutuse of organic solvent, initiator and photochlorination reactor.

For the method for preparing 2-chloro-5-trifluoromethylpyridine providedby the present invention, its chemical reaction formula is as follow:

The present invention provides a technical solution as follow:

A method for preparing 2-chloro-5-trifluoromethylpyridine, the methodcomprises: in presence of a second catalyst, the reaction temperature ismaintained at 150˜350° C., and 3-trifluoromethylpyridine reacts withchlorine gas in the gas phase, to obtain2-chloro-5-trifluoromethylpyridine;

the second catalyst is at least one selected from ZSM-5, 5A, β and 13Xmolecular sieve,

for the ZSM-5 molecular sieve, its Si/Al is 50˜300, the counter cationis at least one selected from H⁺, Na⁺, K⁺, Ca²⁺.

For the preparing method provided by the present invention, the catalystused is at least one selected from ZSM-5, 5A, β and 13X molecular sieve.

When the second catalyst is the ZSM-5 molecular sieve, as a preferredembodiment, its Si/Al ratio is 50˜300, the counter cation is at leastone selected from H⁺, Na⁺, K⁺, Ca²⁺.

As a further preferred embodiment, for the ZSM-5 molecular sieve, itsSi/Al ratio is 80˜200, the counter cation is at least one selected fromH⁺, Na⁺and K⁺.

For the preparing method provided by the present invention, the reactiontemperature may be one that facilitates the reaction.

Preferably, the reaction temperature is 150˜350° C.

Further preferably, the reaction temperature is 200˜300° C.

For the preparing method provided by the present invention provide, themolar ratio of 3-trifluoromethylpyridine to chlorine gas may be one thatfacilitates the reaction.

Preferably, the molar ratio of the 3-trifluoromethylpyridine to chlorinegas is 1:0.1˜20.

Further preferably, the molar ratio of the 3-trifluoromethylpyridine tochlorine gas is 1:0.5˜5.

For the preparing method provided by the present invention, the contacttime of 3-trifluoromethylpyridine with chlorine gas within the catalystbed may be one that facilitates the reaction.

Preferably, the contact time of the 3-trifluoromethylpyridine withchlorine gas within the catalyst bed is 0.5˜100 s.

Further preferably, the contact time of the 3-trifluoromethylpyridinewith chlorine gas within the catalyst bed is 15˜70 s.

For the preparing method provided by the present invention, the reactioncan be conducted in the fixed bed or fluidized bed reactor.

Preferably, the reaction is conducted in the fluidized bed reactor.

The material of the reactor may be quartz tube and Inconel alloy, etc.

Compared to the previous method, the above method for preparing2-chloro-5-trifluoromethylpyridine has the following advantages: highselectivity of the desired product 2-chloro-5-trifluoromethylpyridine,high atom utilization; direct feed of raw material3-trifluoromethylpyridine, without need to use an organic diluent,without need of vaporization and separation on the diluent; low reactiontemperature, small energy consumption.

The present invention also provides a method for preparing2-chloro-5-trifluoromethylpyridine, it has characteristics such as highconversion of raw material, high desired product selectivity, lowreaction temperature, low energy consumption, easy to separate, andwithout need to use organic solvent, initiator and photochlorinationreactor.

For the method for preparing 2-chloro-5-trifluoromethylpyridine providedby the present invention, its chemical reaction formula is as follow:

The present invention provides a technical solution as follow:

A method for preparing 2-chloro-5-trifluoromethylpyridine, the methodcomprises:

In presence of a third catalyst, the reaction temperature is maintainedat 220˜360° C., 3-trifluoromethylpyridine and chlorine gas are passedthrough a catalyst bed, to obtain 2-chloro-5 -trifluoromethylpyridine;

the third catalyst is selected from fluoride, oxide, hydroxide carbonateor chloride of magnesium, calcium, barium, a supported palladiumcatalyst being supported on activated carbon, alumina or aluminiumfluoride.

For the preparing method provided by the present invention, the thirdcatalyst used is selected from fluoride, oxide, hydroxide, carbonate orchloride of magnesium, calcium, barium, a supported palladium catalystbeing supported on activated carbon, alumina or aluminium fluoride.

the fluoride, oxide, hydroxide, carbonate and chloride of magnesium,calcium, barium can be magnesium fluoride, calcium fluoride, bariumfluoride, magnesium oxide, calcium oxide, barium oxide, magnesiumhydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate,calcium carbonate, barium carbonate, magnesium chloride, calciumchloride, barium chloride.

the supported palladium catalyst being supported on activated carbon,alumina or aluminium fluoride can be a supported palladium catalystbeing supported on activated carbon, a supported palladium catalystbeing supported on alumina, a supported palladium catalyst beingsupported on aluminium fluoride.

As a preferred embodiment, the third catalyst is selected from fluoride,oxide or chloride of magnesium, calcium, a palladium catalyst beingsupported on activated carbon or aluminium fluoride.

When the third catalyst used is the supported palladium catalyst beingsupported on activated carbon, alumina or aluminium fluoride, the masspercentage of in the catalyst may be one that facilitates the reaction.

Preferably, the mass percentage of the palladium in the catalyst is0.1˜10 wt %. Further preferably, the mass percentage of the palladium inthe catalyst is 0.5˜3 wt %.

When the third catalyst used is the supported palladium catalyst beingsupported on activated carbon, alumina or aluminium fluoride, as apreferred embodiment, an activating pretreatment is conducted beforeuse.

the activating pretreatment can be an activating pretreatment againstthe supported palladium catalyst by using nitrogen gas and/or chlorinegas at a temperature of 120˜350° C.

For the preparing method provided by the present invention, the reactiontemperature may be one that facilitates the reaction.

Preferably, the reaction temperature is 220˜360° C.

Further preferably, the reaction temperature is 270˜320° C.

For the preparing method provided by the present invention, the molarratio of 3-trifluoromethylpyridine to chlorine gas may be one thatfacilitates the reaction.

Preferably, the molar ratio of the 3-trifluoromethylpyridine to chlorinegas is 1:0.1˜50.

Further preferably, the molar ratio of the 3-trifluoromethylpyridine tochlorine gas is 1:4˜10.

For the preparing method provided by the present invention, the contacttime of 3-trifluoromethylpyridine with chlorine gas within the catalystbed may be one that facilitates the reaction.

Preferably, the contact time of the 3-trifluoromethylpyridine withchlorine gas within the catalyst bed is 1˜60 s.

Further preferably, the contact time of the 3-trifluoromethylpyridinewith the chlorine gas within the catalyst bed is 5˜30 s.

For the preparing method provided by the present invention, the reactioncan be conducted in a fixed bed or fluidized bed reactor.

Preferably, the reaction is conducted in the fluidized bed reactor.

For the preparing method provided by the present invention, the productobtained is washed with water and alkaline solution and distilled, toobtain an oily product, i.e. 2-chloro-5 -trifluoromethylpyridine.

Since under the given reaction condition, the conversion of3-trifluoromethylpyridine in the following examples are all 100%, in thepresent invention the yield of the desired product is the selectivity ofthe desired product.

Compared to the previous method for preparing2-chloro-5-trifluoromethylpyridine, the above method has the followingadvantages: high selectivity of the desired product2-chloro-5-trifluoromethylpyridine, high atom utilization; direct feedof raw material 3-trifluoromethylpyridine, without need to use anorganic diluent, without need to conduct additional vaporization andseparation against the diluent; low reaction temperature, and smallenergy consumption.

DETAILED DESCRIPTION

The present invention will be further described below in conjunctionwith the specific examples, but the present invention is not restrictedby these specific examples. Those skilled in the art should recognizethat, the present invention covers all alternatives, improvements andequivalent that may be included in the claims.

EXAMPLE 1

2-chloro-5-trifluoromethylpyridine (90.8 g, 0.5 mol) and 15% WCl₆/AC(WCl₆ supported on activated carbon, the load was 15 wt %, 12 g) wereadded into a 250 mL autoclave (Inconel alloy), after the kettle coverwas installed, a nitrogen gas of 2 MPa was charged and the pressure wasmaintained for 2 h, a leakage detection was conducted to the reactionkettle, after the reaction kettle was confirmed to be gastight, it wasplaced into an ice ethanol bath for cooling, when the reaction kettlewas cooled to 0° C., about 37.5 g of chlorine gas (0.5 mol) was chargedinto the reaction kettle from the reaction kettle gas phase tube, thenthe reaction kettle was placed into a heating jacket with a magneticstirrer, under a stirring condition the reaction system was heated to150° C., at this time the pressure of the reaction system was about 2.0MPa, at this temperature continuously reacted for 20 h. After thereaction was finished, when the temperature of the reaction systemdropped to room temperature, nitrogen gas was charged into the reactionkettle from a liquid phase tube and a replacement was conducted for 30min (the tail gas being replaced out was introduced into a alkalinewashing bottle for absorption, and neutralized), the reaction kettle wasopened, the catalyst and the products were separated by filtration, anda 10 wt % of NaOH solution was added to the products for neutralization,extracted, and liquid separated, to obtain an oily product. The oilyproduct obtained was dried on anhydrous sodium sulfate then weighed andthe mass was 107.0 g, a qualitative analysis was conducted by GC-MS, anda quantitative analysis was conducted by gas chromatography internalstandard method. The conversion of 2-chloro-5-trifluoromethylpyridine aswell as the selectivity and the yield of the chlorination reactionproduct are seen in Table 1.

EXAMPLE 2

The reaction temperature in Example 1 dropped from 150° C. to 100° C.,other reaction condition and product treatment method were same asExample 1. The mass of the finally obtained oily product after dryingwas 91.2 g. The conversion of 2-chloro-5-trifluoromethylpyridine as wellas the selectivity and the yield of the chlorination reaction productsare seen Table 1.

EXAMPLE 3

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12g) in Example 1 was changed to 15% MoCl₅/AC (MoCl₅ supported onactivated carbon, the load was 15 wt %, 12 g), other reaction conditionand product treatment method were same as Example 1. The mass of thefinally obtained oily product after drying was 97.9 g. The conversion of2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction product are seen in Table 1.

EXAMPLE 4

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% FeCl₃/AC (FeCl₃ supported onactivated carbon, the load was 15 wt %, 12 g), other reaction conditionand the product treatment method were same as Example 1. The mass of thefinally obtained oily product after drying was 107.2 g. The conversionof 2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction product are seen Table 1.

EXAMPLE 5

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% CuCl₂/AC (CuCl₂ supported onactivated carbon, the load was 15 wt %, 12 g), other reaction conditionand the product treatment method were same as Example 1. The mass of theoily product finally obtained after drying was 100.9 g. The conversionof 2-chloro-5-trifluoromethylpyridineas well as the selectivity and theyield of the chlorination reaction products are seen in Table 1.

EXAMPLE 6

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 5 wt %, 12g) in Example 1 was changed to 15% CuCl/AC (CuCl₂ supported on activatedcarbon, the load was 15 wt %, 12 g), other reaction condition and theproduct treatment method were same as Example 1. The mass of the finallyobtained oily product after drying was 98.1 g. The conversion of2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction products are seen in Table 1.

EXAMPLE 7

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% ZnCl₂/AC (ZnCl₂ supported onactivated carbon, the load was 15 wt %, 12 g), other reaction conditionand the product treatment method were same as Example 1. The mass of thefinally obtained oily product after drying was 100.7 g. The conversionof 2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of chlorination reaction product are seen in Table 1.

EXAMPLE 8

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% AlCl₃/AC (AlCl₃ supported onactivated carbon, the load was 15 wt %, 12 g), other reaction conditionand the product treatment method were same as Example 1. The mass of thefinally obtained oily product after drying was 105.2 g. The conversionof 2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction product are seen in Table 1.

EXAMPLE 9

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15 wt % NaY/AC (NaY zeolite molecularsieve supported on activated carbon, the load was 15 wt %, Si/Al ofNaY=5.4,12 g), other reaction condition and the product treatment methodwere same as Example 1. The mass of finally obtained oily product afterdrying was 103.5 g. The conversion of2-chloro-5-trifluoromethylpyridineas well as the selectivity and theyield of the chlorination reaction products are seen in Table 1.

EXAMPLE 10

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% HPW/AC (phosphotungstic acidsupported on activated carbon, the load was 15 wt %, 12 g), otherreaction condition and the product treatment method were same asExample 1. The mass of the finally obtained oily product after dryingwas 106.8 g. The conversion of 2-chloro-5-trifluoromethylpyridine aswell as the selectivity and the yield of the chlorination reactionproduct are seen in Table 1.

EXAMPLE 11

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% HSiW/AC (silicotungstic acidsupported on activated carbon, the load was 15 wt %, 12 g), otherreaction condition and the product treatment method were same asExample 1. The mass of the finally obtained oily product after dryingwas 93.2 g. The conversion of 2-chloro-5-trifluoromethylpyridine as wellas the selectivity and the yield of the chlorination reaction productare seen in Table 1.

EXAMPLE 12

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to 15% HPW/TiO₂ (phosphotungstic acidsupported on TiO₂, the load was 15 wt %, 12 g), other reaction conditionand the product treatment method were same as Example 1. The mass of thefinally obtained oily product after drying was 93.2 g. The conversion of2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction product are seen in Table 1.

EXAMPLE 13

The introducing amount of chlorine gas in Example 1 was increased from35.5 g (0.5 mol) to 71.0 g (1.0 mol), other reaction condition and theproduct treatment method were same as Example 1. The mass of the finallyobtained oily product after drying was 108.7 g. The conversion of2-chloro-5-trifluoromethylpyridine as well as the selectivity and theyield of the chlorination reaction product are seen in Table 1.

Comparative Example 1

15% WCl₆/AC (WCl₆ supported on activated carbon, the load was 15 wt %,12 g) in Example 1 was changed to WCl₆ (non-supported, 1.8 g), otherreaction conditions and the product treatment method were same asExample 1. The mass of finally obtained oily product after drying was98.2 g. The conversion of 2-chloro-5-trifluoromethylpyridine as well asthe selectivity and the yield of the chlorination reaction product areseen in Table 1. Compared to Example 1, it is known that when the activecomponent was not supported on AC, not only the conversion of2-chloro-5-trifluoromethylpyridine was decreased from 99.9% to 65.2%,but also the selectivity of the desired product2,3-dichloro-5-trifluoromethylpyridine was significantly reduced from92.1% to 65.7%. It is seen that supporting the metal chloride on acarrier with high specific surface area can significantly improve itscatalytic performance.

Comparative Example 2

The reaction temperature in Example 1 was raised from 150° C. to 200°C., other reaction condition and the product treatment method were sameas Example 1. The mass of the finally obtained oily product after dryingwas 109.5 g. The conversion of 2-chloro-5-trifluoromethylpyridine aswell as the selectivity and the yield of chlorination reaction productare seen in Table 1.

TABLE 1 conversion of selectivity % 2,5- 2,3,5- 2,6,3- 2,3,6,5- ExampleCTF % DCTF DCTF TCTF other 1 99.9 92.1 4.6 1.2 2.1 2 10.2 88.2 1.2 0.510.1 3 40.5 90.3 3.0 1.3 5.4 4 92.9 87.1 8.4 1.8 2.7 5 56.2 82.7 0.6 4.911.8 6 53.2 85.9 3.0 1.3 6.3 7 65.5 90.4 1.6 1.6 6.5 8 79.9 85.9 7.1 1.95.1 9 55.3 88.6 5.2 0.7 2.4 10 98.7 90.6 0 2.3 7.0 11 39.9 94.9 0 0.94.2 12 19.8 86.4 9.1 0.8 3.7 13 100.0 91.2 3.2 2.5 3.1 Comparative 65.265.7 5.2 2.1 7.0 Example 1 Comparative 100.0 60.2 10.3 23.0 6.5 Example2

EXAMPLE 14

The internal diameter of the heating furnace was 30 mm, and the heightwas 600 mm, the upper and lower two stages were respectively temperaturecontrolled. The upper stage was the chlorofluorination reaction region,and the lower stage was the chlorination reaction region. The internaldiameter of the reaction tube was 19 mm, the length was 700 mm, and thematerial was stainless steel, the catalyst loading heights in the upperand lower two-stage were all 140 mm, and ensuring that the catalyst bedsin the upper and the lower two stages were respectively in a constanttemperature zone of the upper and lower two-stage heating furnace. Thechlorofluorination catalyst bed was composed of 55.5% MgF₂-40.0%Co₂O₃-0.55% CeO₂ (55.5%, 40%, 0.5% are mole percentage of the metalatoms, they are the ratio of metal atom moles of each component to sumof moles of the metal atoms, the composition of the chlorofluorinationcatalyst was shown as the molar ratio of metal atoms, the same below) ofcatalyst. The catalyst was molded into a cylinder having a diameter of3mm and a height of 4 mm. The chlorination catalyst bed was composed of1% Pd/activated carbon (1% being the mass ratio of metal palladium inthe catalyst after calcination, the compositions of the supportedchlorination catalyst are shown as the ratio of the mass of metal atomto the total mass of the catalyst, the same below) of catalyst, thecatalyst was molded into a cylinder having a diameter of 3 mm and aheight of 4 mm.

The chlorofluorination reaction region was heated to 235° C., and thechlorination reaction region was heated to 290° C. The feed rate ofanhydrous hydrogen fluoride was controlled at 10.00 g/h (0.500 mol/h),the catalyst was activated by introducing HF for 3 h, then the3-methylpyridine being vaporized by using nitrogen gas as the carriergas and chlorine gas were introduced into the reaction tube. Wherein,the flowrate of 3-methylpyridine was controlled at 4.00 g/h (0.043mol/h), the flowrate of chlorine gas was controlled at 7.7 L/h (0.344mol/h), the flowrate of nitrogen gas was maintained at 12.0 L/h (0.536mol/h). The molar feed ratio of the reactants was3-methylpyridine:chlorine gas:hydrogen fluoride:nitrogengas=1:8:11.6:12.5. The contact time of all starting reaction materialwith the chlorofluorination catalyst bed and the chlorination catalystbed catalyst were all 4.5 s, and reacted for 8 h.

The tail gas leaving the reaction tube was introduced into water awashing tower and an alkaline washing tower for condensation. The oillayer obtained was separated then neutralized with aqueous ammonia, anda steam distillation was conducted to obtain an oily product. The oilyproduct obtained was dried on anhydrous sodium sulfate then weighed andthe mass was 63.04 g, a quantitative analysis was conducted by gaschromatography internal standard method, and the mass content of 2,5-CTFwas 70.8%, and the reaction yield was 71.5% (calculated on basis of3-MP, the same below).

EXAMPLE 15

the upper stage in the reaction tube in Example 1 was filled with 55.5%MgF₂-40% ZnO-0.5% K₂O catalyst, the catalyst was molded into a cylinderhaving a diameter of 3 mm and a height of 4 mm, the lower stage isfilled with 2% Pd/activated carbon catalyst, the catalyst was moldedinto a cylinder having a diameter of 3 mm and a height of 4 mm.

The chlorofluorination reaction region was heated to 265° C., and thechlorination reaction region was heated to 320° C. The feed rate ofanhydrous hydrogen fluoride was 10.00 g/h (0.500 mol/h), the catalystwas activated by introducing HF for 3 h, then 3-methylpyridine beingvaporized by using nitrogen gas as the carrier gas and chlorine gas wereintroduced into the reaction tube. Wherein, the flowrate of3-methylpyridine was controlled at 4.00 g/h (0.043 mol/h), the flowrateof chlorine gas was controlled at 7.7 L/h (0.344 mol/h), the flowrate ofnitrogen gas was maintained at 12.0 L/h (0.536 mol/h). The molar feedratio of the reactants was 3-methylpyridine:chlorine gas:hydrogenfluoride:nitrogen gas=1:8:11.6:12.5, the contact time of all startingreaction material with the chlorofluorination catalyst bed and thechlorination catalyst bed catalyst were all 4.5 s, and reacted for 8 h.

The treatment method of the tail gas leaving the reaction was same asExample 1. 64.35 g of oily product was obtained, and a gaschromatography analysis was conducted, the mass content of 2,5-CTF was65.7%, and the reaction yield was 67.8%.

EXAMPLE 16

the upper stage in the reaction tube in Example 14 was filled with 77.0%MgF₂-20.0% Bi₂O₃-2.0% Na₂O catalyst, the catalyst was molded into acylinder having a diameter of 3 mm and a height of 4 mm, the lower stagewas filled with MgF₂ catalyst, the catalyst was molded into a cylinderhaving a diameter of 3 mm and a height of 4 mm.

The chlorofluorination reaction region was heated to 220° C., and thechlorination reaction region was heated to 280° C. The feed rate ofanhydrous hydrogen fluoride was controlled at 10.00 g/h (0.500 mol/h),the catalyst was activated by introducing HF for 3 h, then3-methylpyridine being vaporized by using nitrogen gas as the carriergas and chlorine gas were introduced into the reaction tube. Wherein,the flowrate of 3-methylpyridine was controlled at 4.00 g/h (0.043mol/h), the flowrate of chlorine gas was controlled at 7.7 L/h (0.344mol/h), the flowrate of nitrogen gas was maintained at 12.0 L/h (0.536mol/h). Molar feed ratio of the reactants was 3-methylpyridine:chlorinegas:hydrogen fluoride:nitrogen gas=1:8:11.6:12.5, the contact time ofall starting reaction material with the chlorofluorination catalyst bedand chlorination catalyst bed catalyst were all 4.5 s, and reacted for 8h. The treatment method of the tail gas leaving the reaction tube wassame as Example 14. 61.94 g of oily product was obtained, and gaschromatography analysis was conducted, the mass content of 2,5-CTF was77.2%, and reaction yield was 76.7%.

EXAMPLE 17

the upper stage of the reaction tube in Example 14 was filled with 85.0%CrF₃-10.0% CuO-5.0% La₂O₃ catalyst, the catalyst was molded into acylinder having a diameter of 3 mm and a height of 4 mm, the lower stagewas filled with MgO catalyst, the catalyst was molded into a cylinderhaving a diameter of 3 mm and a height of 4 mm.

The chlorofluorination reaction region was heated to 235° C., and thechlorination reaction region was heated to 300° C. The feed rate ofanhydrous hydrogen fluoride was controlled at 10.32 g/h (0.516 mol/h),the catalyst was activated by introducing HF for 3 h, then3-methylpyridine and chlorine gas being vaporized by using nitrogen gasas the carrier gas and chlorine gas were introduced into the reactiontube. Wherein, the flowrate of 3-methylpyridine was controlled at 4.00g/h (0.043 mol/h), the flowrate of chlorine gas was controlled at 8.7L/h (0.387 mol/h), the flowrate of nitrogen gas was maintained at 12.0L/h (0.536 mol/h). Molar feed ratio of the reactants was3-methylpyridine:chlorine gas:hydrogen fluoride:nitrogengas=1:9:12:12.5, the contact time of all starting reaction material withthe chlorofluorination catalyst bed and chlorination catalyst bedcatalyst were all 4.0 s, and reacted for 6 h.

The treatment method of the tail gas leaving the reaction tube was sameas Example 1. 40.50 g of oily product was obtained, and a gaschromatography analysis was conducted, the mass content of 2,5-CTF was69.7%, the reaction yield was 74.5%.

EXAMPLE 18-20

Except for the catalyst, all operation condition was same as Example 16.In Example 18, the upper stage in the reaction tube was filled with90.0% CrF₃-8.0% Fe₂O₃-2.0% La₂O₃ catalyst, the lower stage was filledwith BaCl₂ catalyst; in Example 19, the upper stage in the reaction tubewas filled with 90.0% AlF₃-8.0% NiO-2.0% BaO catalyst, the lower stagewas filled with CaCl₂ catalyst; in Example 20, the upper stage in thereaction tube was filled with 90.0% CrF₃-8.0% NiO-2.0% Na₂O catalyst,the lower stage was filled with 1.5% Pd/activated carbon catalyst.

The reaction respectively obtained 64.30 g, 65.34 g, 64.80 g of oilyproducts, and gas chromatography analysis were conduct, the mass contentof 2,5-CTF were respectively 73.2%, 69.9%, 73.3%, the reaction yieldwere respectively 75.5%, 73.2%, 76.1%.

EXAMPLE 21

The internal diameter of the heating furnace was 35 mm, and the heightwas 500 mm, the upper and lower two stages were respectively temperaturecontrolled. The lower stage was chlorofluorination reaction region, andthe upper stage was chlorination reaction the region. The material ofthe reaction tube was Inconel alloy, the internal diameter of thereaction tube was 30 mm, the length was 600 mm. The lower stage of thereaction tube was filled with 60 mL of 85% AlF₃-10% Mn₂O₃-5% BaO (meandiameter being 0.15 mm) chlorofluorination catalyst, the height of thestatic bed was 89 mm, the upper stage of the reaction tube was filledwith 60 mL of 1% Pd/activated carbon (mean diameter being 0.15 mm)chlorination catalyst, the height of the static bed was 89 mm.Distribution plates were placed at bottom of the reactor and middle ofthe reactor, for distribution of the gas flow and isolation and supportof the catalyst. After 1 h of fluidization with nitrogen gas at 235° C.HF was charged at a feed rate of 8.59 g/h (0.430 mol/h) for 4 h,fluorination was conduted to the catalyst. Then, 3-methylpyridine beingvaporized by using nitrogen gas as the carrier gas and chlorine gas wereintroduced into the reaction tube. Wherein, the flowrate of3-methylpyridine was controlled at 4.00 g/h (0.043 mol/h), the flowrateof chlorine gas was controlled at 5.77 L/h (0.258 mol/h), and theflowrate of nitrogen gas was maintained at 9.62 L/h (0.430 mol/h). Themolar feed ratio of the reactants was 3-methylpyridine:chlorinegas:hydrogen fluoride:nitrogen gas=1:6:10:10, the contact time of allstarting reaction materials with the chlorofluorination catalyst bed andthe chlorination catalyst bed catalyst were all 5.5 s, and reacted for24 h. The tail gas leaving the reaction tube was introduced into thewater washing tower and the alkaline washing tower for condensation. Theoil layer obtained was separated then neutralized with aqueous ammonia,and a steam distillation was conducted to obtain an oily product. Theoily product obtained was dried on anhydrous sodium sulfate then weighedand the mass was 166.49 g, a quantitative analysis was conducted by gaschromatography internal standard method, the mass content of 2,5-CTF was67.3%, and the reaction yield was 73.9%.

EXAMPLE 22

Except that the catalyst was different, other condition was same asExample 21. The lower stage of the reaction tube was filled with 60 mLof 90% AlF₃-9% ZnCl₂-1% CaO (mean diameter being 0.15 mm)chlorofluorination catalyst, the upper stage was filled with 60mL of 1%Pd/Al₂O₃ (mean diameter being 0.15 mm) chlorination catalyst. Theproduct treatment and the analysis method were same as Example 21, toobtain 158.90 g of an oily product, the mass content of 2,5-CTF was68.8%, and the reaction yield was 72.1%.

EXAMPLE 23

A stainless steel tube with a reaction tube internal diameter of 25 mmand length of 800 mm was used as the fixed bed reactor, and HZSM-5molecular sieve with a volumn of 40 mL and a particle size of 5-10 meshand Si/Al ratio of 100 (which means that H⁺ is the counter cation) wasfilled into middle of the fixed bed reactor, a reaction tube line waslinked, and nitrogen gas was introduced for purge, the flowrate ofnitrogen gas was 100 mL/min. The reaction furnace was heated up to 290°C. at a heating rate of 5° C./min, after the catalyst bed reached thereaction temperature nitrogen gas purge was stopped and changed tointroduction of chlorine gas for purge, meanwhile3-trifluoromethylpyridine was continuously introduced into the fixed bedreactor, to initiate the reaction. The molar ratio of the reaction rawmaterial 3-trifluoromethylpyridine to chlorine gas was 1:2, the contacttime of the reactants within the catalyst bed was 30.9 s. The reactionproduct was condensed by an ice water bath then collected in acollection bottle, to obtain an oily product. After the reaction wasfinished, water washing and alkaline washing and acid-removal wereconducted to the oily product, then dried on anhydrous sodium sulfateand distillation was conducted, a qualitative analysis was conducted tothe distillate by GC-MS, a quantitative analysis was conducted to thedistillate composition by gas chromatography internal standard method.

After the quantitative analysis, the reaction results were: theconversion of 3-trifluoromethylpyridine was 98.7%, and the selectivityof 2-chloro-5-trifluoromethylpyridine was 93.8%.

EXAMPLE 24

Except for the catalyst, other condition was same as Example 23, thecatalyst used was 5A molecular sieve.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 89.2%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 89.0%.

EXAMPLE 25

Except for the catalyst, other condition was same as Example 23, thecatalyst used was 13X molecular sieve.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridinecon was 91.5%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 88.3%.

EXAMPLE 26

Except for the catalyst, other condition was same as Example 23, thecatalyst used was β molecular sieve.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 92.3%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 89.2%.

EXAMPLE 27

Except for the reaction temperature, other condition was same as Example23, the reaction temperature was 350° C.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 99.9%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 87.1%.

EXAMPLE 28

The material of the reaction tube was Inconel alloy, the internaldiameter of the reaction tube was 30 mm, the length was 400 mm. Thereaction tube was filled with 60mL of HZSM-5 molecular sieve catalystwith a mean diameter of 0.15 mm and a Si/Al ration of 100, after 1 h offluidization with nitrogen gas at 235° C., it was heated up to 290° C.at a heating rate of 5° C./min, after the catalyst bed reached thereaction temperature the nitrogen gas purge was stopped and changed tointroduction of chlorine gas for purge, meanwhile3-trifluoromethylpyridine was continuously introduced into the fixed bedreactor, to initiate the reaction. The molar ratio of reaction rawmaterial 3-trifluoromethylpyridine to chlorine gas was 1:2, and thecontact time of the reactants within the catalyst bed was 58.5 s. Thereaction product was condensed by an ice water bath then collected in acollection bottle, to obtain an oily matter. After the reaction wasfinished, water washing and alkaline washing and acid-removal wereconducted against the oily matter, dried on anhydrous sodium sulfatethen distillation was conducted, a qualitative analysis was conducted tothe distillate by GC-MS, a quantitative analysis was conducted to thedistillate composition by gas chromatography internal standard method.

After the quantitative analysis, the reaction results were: the versionof 3-trifluoromethylpyridinecon was 97.9%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 94.5%.

EXAMPLE 29

Except for the catalyst, other condition were same as Example 28, thecatalyst used was HZSM-5 molecular sieve with Si/Al=50.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 99.0%, the selectivity of2-chloro-5-trifluoromethylpyridine was 90.1%.

EXAMPLE 30

Except for the catalyst, other condition was same as Example 28, thecatalyst used was NaZSM-5 (which means Na⁺ is the counter cation)molecular sieve with Si/Al=100.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 95.7%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 92.5%.

EXAMPLE 31

Except for the catalyst, other condition was same as Example 28, thecatalyst used was Si/Al=100 of KZSM-5 (which means K⁺ is the countercation) molecular sieve.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 92.3%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 92.0%.

EXAMPLE 32

Except for the catalyst, other condition was same as Example 28, thecatalyst used was CaZSM-5 (which means Ca⁺ is the counter cation)molecular sieve with a Si/Al=100.

After a quantitative analysis, the reaction result were: the conversionof 3-trifluoromethylpyridine was 4.4%, the selectivity of2-chloro-5-trifluoromethylpyridine was 88.1%.

EXAMPLE 33

Except for the chlorine gas ratio, other condition was same as Example23, the molar ratio of raw material 3-trifluoromethylpyridine tochlorine gas was 1:10.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 98.5%, and the selectivity of2-chloro-5-trifluoromethylpyridine was 85.2%.

Comparative Example 3

The catalyst in Example 23 was changed to a HZSM-5 molecular sieve withSi/Al of 22, other condition was unchanged.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 99.9%, but the selectivity of thedesired product 2-chloro-5-trifluoromethylpyridine was only 47.3%.

Comparative Example 4

According to the disclosure in China CN104610137 a FeCl₃/activatedcarbon catalyst was used as the catalyst, and the reaction temperaturewas controlled at 250° C., other operation condition was consistent withExample 23.

After a quantitative analysis, the reaction results were: the conversionof 3-trifluoromethylpyridine was 96.2%, the selectivity of the desiredproduct 2-chloro-5-trifluoromethylpyridine was only 20.2%.

EXAMPLE 34

The internal diameter of the heating furnace was 30 mm, and the heightwas 600 mm. The internal diameter of the reaction tube was 19 mm, andthe length was 700 mm, the material was stainless steel, the loadingheight of the catalyst was 140 mm. The catalyst bed was composed of 1%Pd/activated carbon (1% being the mass ratio of metal palladium in thecatalyst after calcination, the composition of the supportedchlorination catalyst are all shown as the ratio of mass of metal atomto total mass of the catalyst, the same below) catalyst, the catalystwas molded into a cylinder having a diameter of 3 mm and a height of 4mm. The reaction region was heated to 290° C., the vaporized3-trifluoromethylpyridine and chlorine gas were introduced into thereaction tube. Wherein, the flowrate of 3-trifluoromethylpyridine wascontrolled at 6.33 g/h (0.043 mol/h), the flowrate of chlorine gas wascontrolled at 7.7 L/h (0.344 mol/h). Molar feed ratio of the reactantswas 3-trifluoromethylpyridine:chlorine gas=1:8, the contact time of allstarting reaction material with the catalyst bed were 16.5 s, andreacted for 8 h.

The tail gas leaving the reaction tube was introduced into the waterwashing tower and the alkaline washing tower for condensation. The oillayer obtained was separated then neutralized with aqueous ammonia, anda steam distillation was conducted to obtain an oily product. The oilyproduct obtained was dried on anhydrous sodium sulfate then weighed andthe mass was 66.28 g, a quantitative analysis was conducted by gaschromatography internal standard method, the mass content of2-chloro-5-trifluoromethylpyridine was 88.7%, and the yield was 94.1%(calculated relative to 3-trifluoromethylpyridine, the same below).

EXAMPLE 35

the reaction tube in Example 34 was filled with 2% Pd/activated carboncatalyst, the catalyst was molded into a cylinder having a diameter of3mm and a height of 4mm. The reaction region was heated to 320° C. Thevaporized 3-trifluoromethylpyridine and chlorine gas were introducedinto the reaction tube. Wherein, the flowrate of3-trifluoromethylpyridine was controlled at 6.33 g/h (0.043 mol/h), theflowrate of chlorine gas was controlled at 7.7 L/h (0.344 mol/h). Molarfeed ratio of the reactants was 3-trifluoromethylpyridine: chlorinegas=1:8, the contact time of all starting reaction materials with thecatalyst bed were 16.5 s, and reacted for 8 h.

The treatment method of the tail gas leaving the reaction tube was sameas Example 34, to obtain 67.59 g of an oily product, and a gaschromatography analysis was conducted, the mass content of2-chloro-5-trifluoromethylpyridine was 84.8%, and the yield was 91.7%.

EXAMPLE 36

the reaction tube in Example 34 was filled with MgF₂ catalyst, thecatalyst was molded into a cylinder having a diameter of 3 mm and aheight of 4 mm. The reaction region was heated to 280° C. The vaporized3-trifluoromethylpyridine and chlorine gas were introduced into thereaction tube. Wherein, the flowrate of 3-trifluoromethylpyridine wascontrolled at 6.33 g/h (0.043 mol/h), the flowrate of chlorine gas wascontrolled at 7.7 L/h (0.344 mol/h). Molar feed ratio of the reactantswas 3-trifluoromethylpyridine:chlorine gas=1:8, the contact time of allstarting reaction material with the catalyst bed were 16.5 s, andreacted for 8 h.

The treatment method of the tail gas leaving the reaction tube was sameas Example 34, to obtain 65.86 g of an oily product, and a gaschromatography analysis was conduct, the mass content of2-chloro-5-trifluoromethylpyridineof was 87.8%, and the yield was 92.5%.

EXAMPLE 37

the reaction tube in Example 34 was filled with a MgO catalyst, thecatalyst was molded into a cylinder having a diameter of 3 mm and aheight of 4 mm. The reaction region was heated to 300° C. The vaporized3-trifluoromethylpyridine and chlorine gas were introduced into thereaction tube. Wherein, the flowrate of 3-trifluoromethylpyridine wascontrolled at 6.33 g/h (0.043 mol/h), the flowrate of chlorine gas wascontrolled at 8.7 L/h (0.387 mol/h). Molar feed ratio of the reactantswas 3-trifluoromethylpyridine=1:9, the contact time of all startingreaction material with the catalyst bed were 14.8 s, and reacted for 6h.

The treatment method of the tail gas leaving the reaction tube was sameas Example 34. 48.49 g of an oily product was obtained, and a gaschromatography analysis was conducted, the mass content of2-chloro-5-trifluoromethylpyridine was 86.7%, and the yield was 89.6%.

EXAMPLE 38-40

Except for the catalyst, all operation condition was same as Example 35.In Example 38, the reaction tube was filled with BaCl₂ catalyst; inExample 39, the reaction tube was filled with CaCl₁₂ catalyst; inExample 40, the reaction tube was filled with 1.5% Pd/activated carboncatalyst. The reaction respectively obtained 66.25 g, 61.49 g, 64.57 gof oily products, and gas chromatography analysis were conducted, themass content of 2-chloro-5-trifluoromethylpyridine were respectively85.0%, 89.5%, 89.8%, and the yield were respectively 90.1%, 88.0%,92.8%.

EXAMPLE 41

Internal diameter of the heating furnace was 35 mm, the height was 500mm. The material of the reaction tube was Inconel alloy, the internaldiameter of the reaction tube was 30 mm, and the length was 600 mm. Thereaction tube was filled with 60 mL of 1% Pd/activated carbon (meandiameter being 0.15 mm) chlorination catalyst, the height of the staticbed was 89 mm. After 1 h of fluidization with nitrogen gas at 235° C.,the vaporized 3-trifluoromethylpyridine and chlorine gas were introducedinto the reaction tube. Wherein, the flowrate of3-trifluoromethylpyridine was controlled at 6.33 g/h (0.043 mol/h), theflowrate of chlorine gas was controlled at 5.77 L/h (0.258 mol/h), theflowrate of nitrogen gas was maintained at 9.62 L/h (0.430 mol/h). Molarfeed ratio of the reactants was 3-trifluoromethylpyridine: chlorinegas=1:6, the contact time of all starting reaction materials with thecatalyst bed was 13.5s, and reacted for 24 h.

The tail gas leaving the reaction tube was introduced into the waterwashing tower and the alkaline washing tower for condensation. The oillayer obtained was separated then neutralized with aqueous ammonia, anda steam distillation was conducted against the oily product obtained.The oily product obtained was dried on anhydrous sodium sulfate thenweighed and the mass was 185.88 g, a quantitative analysis was conductedby gas chromatography internal standard method, the mass content of2-chloro-5-trifluoromethylpyridine was 95.8%, and the yield was 94.9%.

EXAMPLE 42

Except that catalyst was different, other condition was same as Example41. The reaction tube was filled with 60 mL of 1% Pd/Al₂O₃ (meandiameter being 0.15 mm) chlorination catalyst. The product treatment andanalysis method were same as Example 38, to obtain 179.69 g of an oilyproduct, by chromatography analysis the mass content of2-chloro-5-trifluoromethylpyridine was 94.6%, and the yield was 90.7%.

The above preparing method of 2,3-dichloro-5-trifluoromethylpyridineprovided by the present invention significantly increases the yield andthe selectivity of the desired product2,3-dichloro-5-trifluoromethylpyridine. The selectivity of2,3-dichloro-5-trifluoromethylpyridine can substantially reach at least82% or more. The method provided by the present invention not onlyreduces the unit consumption of the product, and reduces separationcost, but also the reaction temperature is much lower than 400° C., themethod can significantly reduce energy consumption and improve safety.

1. A method for preparing 2,3-dichloro-5-trifluoromethylpyridine,wherein the method comprises: at a temperature of 100˜150° C. and apressure of 0.5˜5.0 MPa, in the presence of a first catalyst,2-chloro-5-trifluoromethylpyridine reacts with chlorine gas to obtain2,3-dichloro-5-trifluoromethylpyridine; the first catalyst is supportedmetal chloride; for the supported metal chloride, its active componentsare at least one selected from WCl₆, MoCl₅, FeCl₃, AlCl₃, CuCl₂, ZnCl₂,SnCl₄, and SbCl₅, and the loading of the active components is 1-50 wt %;the 2-chloro-5-trifluoromethylpyridine is prepared by the followingsteps: in the presence of a second catalyst, the reaction temperature ismaintained at 150˜350° C., and 3-trifluoromethylpyridine reacts withchlorine in gaseous phase, to obtain 2-chloro-5-trifluoromethylpyridine;the second catalyst is at least one selected from ZSM-5,5A, β and 13Xmolecular sieve, for the ZSM-5 molecular sieve, its Si/Al ratio is50˜300, the counter cation is at least one selected from H⁺, Na⁺, K⁺,Ca²⁺.
 2. The method for preparing 2,3-dichloro-5-trifluoromethylpyridineaccording to claim 1, wherein the reaction pressure is 1.0˜2.0 MPa. 3.The method for preparing 2,3-dichloro-5-trifluoromethylpyridineaccording to claim 1, wherein for the supported metal chloride, itsactive components are at least one selected from WCl₆, MoCl₅, ZnCl₂,FeCl₃, and the loading of the active components is 5-20 wt %.
 4. Themethod for preparing 2,3-dichloro-5-trifluoromethylpyridine according toclaim 1, wherein the first catalyst support is at least one selectedfrom of silica, alumina, titania, zirconia, activated carbon, siliconcarbide and mesoporous molecular sieve.
 5. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to claim 1, wherein theamount of the first catalyst is 0.1-30 wt % of the mass of2-chloro-5-trifluoromethylpyridine, the molar ratio of chlorine to2-chloro-5-trifluoromethylpyridine is 0.5˜10:1.
 6. The method forpreparing 2,3-dichloro-5-trifluoromethylpyridine according to claim 5,wherein the amount of the first catalyst is 5˜20 wt % of the mass of2-chloro-5-trifluoromethylpyridine, and the molar ratio of chlorine to2-chloro-5-trifluoromethylpyridine is 1˜3:1.
 7. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to claim 1, wherein thereaction of 2-dichloro-5-trifluoromethylpyridine is conducted in anautoclave, the material of the autoclave is selected from 316L, Monelalloy, Inconel alloy or Hastelloy alloy.
 8. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to claim 1, whereinafter the reaction is finished, an alkaline solution is added, thenseparated to obtain 2,3-dichloro-5-trifluoromethylpyridine.
 9. Themethod for preparing 2,3-dichloro-5-trifluoromethylpyridine according toclaim 1, wherein for the ZSM-5 molecular sieve, its Si/Al is 80˜200, thecounter cation is at least one selected from H⁺, Na⁺ and K⁺.
 10. Themethod for preparing 2,3-dichloro-5-trifluoromethylpyridine according toclaim 1, wherein the reaction temperature of 3-trifluoromethylpyridinewith chlorine is 200˜300° C.
 11. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to claim 1, wherein themolar ratio of 3-trifluoromethylpyridine to chlorine is 1:0.1˜20. 12.The method for preparing 2,3-dichloro-5-trifluoromethylpyridineaccording to claim 11, wherein the molar ratio of the3-trifluoromethylpyridine to chlorine is 1:0.5˜5.
 13. The method forpreparing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1,wherein the contact time of 3-trifluoromethylpyridine with chlorinewithin the catalyst bed is 0.5˜100 s.
 14. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to claim 13, whereinthe contact time of 3-trifluoromethylpyridine with chlorine within thecatalyst bed is 15˜70 s.
 15. The method for preparing2,3-dichloro-5-trifluoromethylpyridine according to any one of claim 1,wherein the reaction of 3-trifluoromethylpyridine with chlorine isconducted in a fixed bed or fluidized bed reactor.